Engineering Design: Students Create Eye-Socket Implant

After six months in the lab synthesizing polymers for an expandable eye-socket implant, Amanda Christian Th’12, Elizabeth Chang Th’12, and Chris Ng Th’12 traveled to Madurai, India, to present their prototype to project sponsor Aurolab and tour the eye hospital where their research will be implemented.

Aurolab, a nonprofit that makes high-quality, low-cost eye products, wanted the students to improve implants for treating anophthalmia/microphthalmia, a rare condition in which infants are born with no or atrophied eyeballs. Without the eyeball to support it, the facial structure of the skull develops incorrectly and can cause cosmetic and sinus problems later in life. A spherical implant inserted into the eye socket in infancy supports proper skull development. But current spheres do not expand with growth and have to be replaced every month. Christian, Chang, and Ng created a hydrogel sphere that grows with the skull by absorbing fluid from the surrounding tissue, reducing the number of implant surgeries during growth.

The prototype is made from a network of cross-linked synthetic polymers. “Our original idea was to go with natural polymers,” explains Chang, “but it was hard to make them work. One day Professor Van Citters came by and showed us a toy he’d bought for his son. It was an acrylamide whale that expands in water. We all knew acrylamide from electrophoresis gel, but we hadn’t thought about its expansive properties. It was a no-brainer once it was pointed out.”

Experimenting with composites of varying amounts of acrylamide and HEMA, a synthetic polymer used in soft contact lenses, the students synthesized a compound that both expands in water and remains stable under pressure comparable to that inside the eye socket. Their prototype costs $8 per sphere to produce, compared to $500 per current state-of-the-art implant.

The trip to Aurolab was eye opening. “They had lots of ideas for us on how to implement and test our research in real bodies,” says Christian.

“Not only did we learn a great deal about materials and chemical engineering,” says Ng, “but we also were able to experience first-hand a new culture and their philosophy on healthcare.”